What's the size of the bolt that fits the 049's prop and aluminum spinner?  I don't want the stock slotted head screw. And I recall I had one where the socket Head of the screw was flush with the top of the aluminum spinner, in other words the spinner was drilled out on the top deep enough to cover the head of the bolt. Who has them, or who makes them? Thanks.       P.S. I modified this post to remove the word HEX. What I meant was the socket type head, typically like the ones we use for our larger engine
 mounting bolts.      Kevin.

The engine is Cox black widow 049.

The Cox .049's use a 5-40 thread. Major diameter is .125"

Haven't seen a spinner like you describe with the recessed screw head.

To keep from breaking so many cranks at the undercut relief for the knurled splines, I have reverted to using a stud and custom made spinner. At least on Mouse Motors. On trainer engines, I still use whatever is handy.

Divot

PS--Looks like Norm beat me to it. He knows his .049s, and proved it by taking a solid second place in Coffee Can Cox Racing here in California.

Any industrial supply store should have them. I'm not talking about Home Depot, though.... Most cities have at least one industrial supply that has a good fastener selection. Or, you can just order them up thru a big house.

For example, McMaster Carr has a wide selection of fasteners if you want to mail order and don't mind the minimum order size. If you go with the length Norm recommended, it'll cost you $5.51 for 50 screws (alloy steel, black oxide finish, no certs) plus taxes, shipping, and coronavirus fees.

https://www.mcmaster.com/screws/socket-head-screws/socket-head-screws-6/alloy-steel-socket-head-screws-8/

Dave

PS--One annoying feature of using socket head cap screws when flying over asphalt is that any minor flip over (like in Mouse racing) may pack the hex recess with asphaltum puckey. If you have a sharp object and a few minutes to pick the crud back out it's not an issue. If you are racing, and broke a prop, you're done--even if the competition is having bad luck and going slow.

  Try the Cox vendors on eBay for the 1" long 5-40 bolts.. Several hobby related fastener suppliers listed in the magazines also.5-40 is a lot more common than you think.
  Type at you later,
  Dan McEntee

Thanks everyone😁👍

USPS must be slow again with pony express riders having to wear masks.   You should be getting a couple of 5-40 screws with a note.